xen/swiotlb: Remove functions not needed anymore.

Sparse warns us off:
drivers/xen/swiotlb-xen.c:506:1: warning: symbol 'xen_swiotlb_map_sg' was not declared. Should it be static?
drivers/xen/swiotlb-xen.c:534:1: warning: symbol 'xen_swiotlb_unmap_sg' was not declared. Should it be static?

and it looks like we do not need this function at all.

Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/swiotlb-xen.c

@@ -515,14 +515,6 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg_attrs);
 
-int
-xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
-		   enum dma_data_direction dir)
-{
-	return xen_swiotlb_map_sg_attrs(hwdev, sgl, nelems, dir, NULL);
-}
-EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg);
-
 /*
  * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
  * concerning calls here are the same as for swiotlb_unmap_page() above.
@@ -543,14 +535,6 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg_attrs);
 
-void
-xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
-		     enum dma_data_direction dir)
-{
-	return xen_swiotlb_unmap_sg_attrs(hwdev, sgl, nelems, dir, NULL);
-}
-EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg);
-
 /*
  * Make physical memory consistent for a set of streaming mode DMA translations
  * after a transfer.